Micro-crystalline diamond (MCD) and diamond like carbon (DLC) thin films were deposited on silicon (100) substrates by hot-filament CVD process using a mixture of CH₄ and H₂ gases at substrate temperature between 400–800°C. The microstructure of the films were studied by X-ray diffraction and scanning electron microscopy. The low temperature deposited films were found to have a mixture of amorphous and crystalline phases. At high temperatures (> 750°C) only crystalline diamond phase was obtained. Scanning electron micrographs showed faceted microcrystals of sizes up to 2µm with fairly uniform size distribution. The structure of DLC films was studied by spectroscopic ellipsometry technique. An estimate of the amount of carbon bonds existing insp² andsp³ form was obtained by a specially developed modelling technique. The typical values ofsp³/sp² ratio in our films are between 1·88–8·02.

A Jobin Yvon-Spex (HR640) monochromator with a notch filter (514·5 nm) and Ar⁺ ion laser has been used to set up a low cost laser Raman spectrometer. The selection and setup of the various optical components used in the present work has been solely carried out in our laboratory. The calibration of the monochromator was established from the studies of various standard mercury lines and the obtained data fitted with the reported data. Raman signals have been recorded for a number of samples e.g. diamond, ruby, carbon tetrachloride (CCI₄), benzene (C₆H₆) and ethanol (C₂H₅OH). The obtained results are found to be in excellent agreement with the reported values for these materials in the literature.